The patch titled Subject: mm/mmap.c: fix mmap return value when vma is merged after call_mmap() has been added to the -mm tree. Its filename is fix-mmap-return-value-when-vma-is-merged-after-call_mmap.patch

This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/fix-mmap-return-value-when-vma-is-... and later at https://ozlabs.org/~akpm/mmotm/broken-out/fix-mmap-return-value-when-vma-is-...

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------------------------------------------------------ From: Liu Zixian liuzixian4@huawei.com Subject: mm/mmap.c: fix mmap return value when vma is merged after call_mmap()

On success, mmap should return the begin address of newly mapped area, but patch "mm: mmap: merge vma after call_mmap() if possible" set vm_start of newly merged vma to return value addr. Users of mmap will get wrong address if vma is merged after call_mmap(). We fix this by moving the assignment to addr before merging vma.

Link: https://lkml.kernel.org/r/20201203085350.22624-1-liuzixian4@huawei.com Fixes: d70cec898324 ("mm: mmap: merge vma after call_mmap() if possible") Signed-off-by: Liu Zixian liuzixian4@huawei.com Cc: Miaohe Lin linmiaohe@huawei.com Cc: Hongxiang Lou louhongxiang@huawei.com Cc: Hu Shiyuan hushiyuan@huawei.com Cc: David Hildenbrand david@redhat.com Cc: Jason Gunthorpe jgg@ziepe.ca Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/mmap.c | 26 ++++++++++++-------------- 1 file changed, 12 insertions(+), 14 deletions(-)

--- a/mm/mmap.c~fix-mmap-return-value-when-vma-is-merged-after-call_mmap +++ a/mm/mmap.c @@ -1808,6 +1808,17 @@ unsigned long mmap_region(struct file *f if (error) goto unmap_and_free_vma;

+ /* Can addr have changed?? + * + * Answer: Yes, several device drivers can do it in their + * f_op->mmap method. -DaveM + * Bug: If addr is changed, prev, rb_link, rb_parent should + * be updated for vma_link() + */ + WARN_ON_ONCE(addr != vma->vm_start); + + addr = vma->vm_start; + /* If vm_flags changed after call_mmap(), we should try merge vma again * as we may succeed this time. */ @@ -1822,25 +1833,12 @@ unsigned long mmap_region(struct file *f fput(vma->vm_file); vm_area_free(vma); vma = merge; - /* Update vm_flags and possible addr to pick up the change. We don't - * warn here if addr changed as the vma is not linked by vma_link(). - */ - addr = vma->vm_start; + /* Update vm_flags to pick up the change. */ vm_flags = vma->vm_flags; goto unmap_writable; } }

- /* Can addr have changed?? - * - * Answer: Yes, several device drivers can do it in their - * f_op->mmap method. -DaveM - * Bug: If addr is changed, prev, rb_link, rb_parent should - * be updated for vma_link() - */ - WARN_ON_ONCE(addr != vma->vm_start); - - addr = vma->vm_start; vm_flags = vma->vm_flags; } else if (vm_flags & VM_SHARED) { error = shmem_zero_setup(vma); _

Patches currently in -mm which might be from liuzixian4@huawei.com are

fix-mmap-return-value-when-vma-is-merged-after-call_mmap.patch